Integrated multi-circuit microchannel heat exchanger

ABSTRACT

A microchannel heat exchanger has at least two manifolds, with the at least two manifolds communicating with a respective one of a first and second plurality of heat exchange tube banks. The first and second plurality of heat exchange tube banks are intertwined within a single microchannel heat exchanger core.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional patent applicationNo. 61/080780, which was filed Jul. 15, 2008.

BACKGROUND OF THE INVENTION

In recent years, much interest and design effort has been focused on theefficient operation of the heat exchangers (and condensers, gas coolersand evaporators in particular) of refrigerant systems. One relativelyrecent advancement in heat exchanger technology is the development andapplication of parallel flow, or so-called microchannel or minichannel,heat exchangers (these two terms will be used interchangeably throughoutthe text), as the condensers, gas coolers and evaporators.

These heat exchangers are provided with a plurality of parallel heatexchange tubes, typically of a non-round shape, among which refrigerantis distributed and flown in a parallel manner. The heat exchange tubesare orientated generally substantially perpendicular to a refrigerantflow direction in inlet, intermediate and outlet manifolds that are inflow communication with the heat exchange tubes. The heat exchange tubestypically have a multi-channel construction, with refrigerantdistributed within these multiple channels in a parallel manner. Heattransfer fins may be inter-disposed and rigidly attached to the heatexchange tubes. The primary reasons for the employment of the parallelflow heat exchangers, which usually have aluminum furnace-brazedconstruction, are related to their superior performance, high degree ofcompactness, structural rigidity, lower weight, lower refrigerant chargeand enhanced resistance to corrosion.

At times, there may be reasons to have multiple distinct refrigerantcircuits within a single heat exchanger core and construction in arefrigerant system. As one example, a dual circuit refrigerant systemhaving two completely separate refrigerant independent circuits withseparate compressors and heat exchangers, etc. can be provided toachieve capacity control and efficiency improvement. In otherapplications, it may be desirable to route the total refrigerant flowonly through a portion of the heat exchanger, while utilizing the entireheat exchanger frontal area. Furthermore, it may be desirable toimplement multiple independent refrigerant paths of a single refrigerantcircuit through the heat exchanger core to improve the heat exchangereffectiveness.

To date, the provision of the multiple distinct refrigerant circuitsutilizing total frontal or cross-sectional area of the heat exchangerhas required distinct heat exchangers, at least when a microchannel heatexchanger is used. More traditional heat exchangers, such as a roundtube and plate fin heat exchangers, can be formed to be of amulti-circuit intertwined configuration utilizing the total frontal areaof the heat exchanger, however, microchannel heat exchangers have notbeen easily tailored to include such multiple circuit configurations.

SUMMARY OF THE INVENTION

A microchannel heat exchanger includes two separate manifolds leadinginto a plurality of separate microchannel tube banks. In embodiments,the separate tube banks extend parallel to each other along a firstdirection through one dimension of a heat exchange area. The banks fromthe at least two manifolds are interspersed along a second directionwhich is perpendicular to the first direction.

These and other features of the present invention can be best understoodfrom the following specification and drawings, the following of which isa brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a 3D view of an inventive heat exchanger.

FIG. 1B shows a first schematic that might utilize the inventive heatexchanger.

FIG. 1C shows a second schematic that might utilize the inventive heatexchanger.

FIG. 2 shows an enlarged manifold section of the FIG. 1A heat exchanger.

FIG. 3 is an end view of FIG. 2.

FIG. 4A shows detail of the manifold section of the inventive heatexchanger.

FIG. 4B shows an alternate feature of the inventive heat exchanger.

FIG. 5 is a cross-sectional view of a heat exchange tube.

FIG. 6A shows a 3D view of another embodiment of the inventive heatexchanger.

FIG. 6B is an end view of the FIG. 6A embodiment.

FIG. 6C shows an enlarged manifold section of the FIG. 6A heatexchanger.

FIG. 7A shows a 3D view of another embodiment of the inventive heatexchanger.

FIG. 7B is an end view of the FIG. 7A embodiment.

FIG. 7C shows an enlarged manifold section of the FIG. 7A heatexchanger.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a microchannel heat exchanger 20 having a heat exchangerfrontal or cross-sectional surface area 21. An inlet pipe 24 suppliesrefrigerant into a first inlet manifold 22, and an inlet pipe 28supplies refrigerant into a second inlet manifold 26. The two inletpipes 24 and 28 can be connected to completely separate independentrefrigerant circuits, or can be connected to a common refrigerant sourceof a single refrigerant circuit. Outlet manifolds 30 and 32 lead tooutlet pipes 29 and 31, communicating the refrigerant downstream toindependent refrigerant circuits or to a single refrigerant circuitrespectively. Although references to a refrigerant and to a refrigerantsystem are made throughout the text, any suitable heat transfer fluid,such as, for instance, water, ethylene glycol, propylene glycol or oil,and an associated system, can be utilized instead. Furthermore, althoughmicrochannel heat exchangers of the invention are schematically shown ina single-pass configuration (see for instance FIG. 1A), any number ofpasses can be implemented in a similar manner, and all such multi-passmicrochannel heat exchangers (see FIG. 4B) are within the scope of theinvention.

When the inlet pipes 24 and 28 and the outlet pipes 29 and 31communicate refrigerant to separate independent refrigerant circuits ofa refrigerant system, capacity control and efficiency improvement areachieved at part-load operation, as the entire frontal surface area 21is utilized in heat transfer interaction with the air flowing acrossheat exchanger external surfaces, while only one of the refrigerantcircuits is operating. When the inlet pipes 24 and 28 and the outletpipes 29 and 31 communicate refrigerant to a single refrigerant circuitof a refrigerant system, at certain conditions, it may be desired toflow refrigerant only through a portion of the heat exchanger 20, whilestill utilizing the entire heat exchanger frontal area 21 for betterperformance. Such conditions may arise, for instance, for the purposesof head pressure control or maintaining minimum refrigerant velocity forproper oil circulation throughout a refrigerant system and return to thecompressor. Furthermore, it may be desirable to implement multipleindependent refrigerant paths of a single refrigerant circuit throughthe heat exchanger core to improve refrigerant distribution and the heatexchanger effectiveness. As known, refrigerant distribution isparticularly important for two-phase refrigerant flows, such as arefrigerant flow entering an evaporator.

FIG. 1B shows a basic exemplary multi-circuit refrigerant system thatmight utilize the inventive heat exchanger 20. In this multi-circuitrefrigerant system, there are two entirely separate independentrefrigerant circuits 300 and 301, each incorporating its own expansiondevice 302, separate evaporator heat exchangers 304 and 308, andseparate compressors 306. As can be appreciated, for both circuits, therefrigerant is routed through the single heat exchanger 20. The FIG. 1Bis quite simplified, and the flow through the heat exchanger 20 can bebetter appreciated from a review of FIG. 1A. However, the power of thissystem configuration to provide the multiple refrigerant circuits, whilestill requiring only a single heat exchange 20 with fully utilizedfrontal area 21, especially for part-load conditions when only some ofthe refrigerant circuits are operational, is apparent. The system may bea heat pump or an air conditioner, and the heat exchanger 20 may be theindoor heat exchanger or the outdoor heat exchanger. In addition, theheat exchanger 20 can be utilized for other applications such as areheat function, as an example, if appropriate refrigerant circuitry isprovided.

FIG. 1C shows yet another application of the inventive heat exchanger20. In this application, a single refrigerant line 401 leads to branchrefrigerant lines 402 and 404, connecting to the refrigerant manifoldsassociated with the inventive heat exchanger 20. Refrigerant flowcontrol devices such as valves 406 control refrigerant flow to thebranch refrigerant lines 402 and 404, and then to the heat exchanger 20.In this manner, the total volume of refrigerant passing through the heatexchanger 20, refrigerant velocity and heat transfer area utilizationfor the heat exchanger 20 can be controlled. The various reasons forproviding such control are known in the art, but the use of amicrochannel heat exchanger providing intertwined refrigerant circuitswithin a single heat exchanger structure is inventive.

FIG. 2 shows a detail of the inlet manifolds 22 and 26. The outletmanifolds 30 and 32 are constructed and connected to the heat exchangercore in a similar manner. As can be appreciated, connecting tubes 33from each manifold 22 and 26 alternatively lead to separate independentbanks of heat exchange tubes 34 extending perpendicular to the plane ofthe frontal heat exchange surface area 21 along a first direction. Eachmanifold has plural connecting tubes 33 connected to plural refrigerantheat exchange tubes 34. As can be appreciated from this figure, the heatexchange tube banks 34 connected to the two manifolds 22 and 26 have analternating pattern along a second direction along the manifold axis,which is generally perpendicular to the first direction. For instance,in some applications, the first direction is a horizontal direction andthe second direction is a vertical direction; in other applications thefirst direction is a vertical direction and the second direction is ahorizontal direction.

FIG. 3 shows the end view of the heat exchanger 20 and its manifolds 22and 26 leading to the connecting tubes 33. Notably, while the manifoldsare shown extending generally vertically, with the heat exchange tubebanks extending generally horizontally, the manifolds can extendgenerally horizontally with the heat exchange tube banks extendinggenerally vertically.

The heat exchanger 20 typically includes external heat transfer fins,like a standard microchannel heat exchanger construction, but they havebeen omitted to simplify the understanding of the drawings.

FIG. 4A shows a detail of the inlet pipe 28 leading into the inletmanifold 26, into the connecting tube 33, and into the bank of heatexchange tubes 34. As known, the heat exchange tube 34 for amicrochannel heat exchanger typically has a plurality of parallelrefrigerant channels 100 separated by dividing walls 101, as shown inFIG. 5. The parallel refrigerant channels 100 each preferably have ahydraulic diameter that is less than 5 mm, and may be less than 3 mm.Notably, the term “hydraulic diameter” does not imply that the channelsare circular in cross-section.

FIG. 4B shows an alternative heat exchanger pass arrangement 200. Thisis a multi-pass heat exchanger construction, wherein the manifolds 22and 30 are actually subdivided into multiple manifold chambers andincorporate inlet and outlet manifold chambers 205 and 206 as well asintermediate manifold chambers 207 and 208 respectively. As an example,refrigerant flows through the heat exchange tube bank 34 extending fromthe inlet manifold chamber 205 of the manifold 22 toward theintermediate manifold chamber 207 of the manifold 30, but then reversesflow direction through another heat exchange tube bank 201 to reach theintermediate manifold chamber 208 of the manifold 22, and then reversesdirection once again to flow through yet another heat exchange tube bank202 to reach the outlet chamber 206 of the manifold 30. Divider plates204 subdivide each of the manifolds 22 and 30 into the manifold chambers205 and 208 and manifold chambers 207 and 208 respectively. Within thisembodiment, heat exchange tube banks of the other refrigerant circuitwould be intertwined with the heat exchange tube banks 34, 201 and 202.FIG. 4B is a very simplified view. As can be appreciated, connectingrefrigerant tubes 33 extending laterally from the manifolds 22 and 30would typically be utilized within this embodiment, but are omitted inthe FIG. 4B for simplicity.

FIGS. 6A and 6B show another embodiment 75 wherein an inlet manifold 82has three adjacent connecting tubes 84, and hence three adjacent heatexchange tubes, and an inlet manifold 80 has only two adjacentconnecting tubes 86, and hence only two adjacent heat exchange tubes. Asbefore, the alternating pattern repeats itself along the manifold axis.In this manner, the relative size of the heat exchanger portionconnected to each inlet manifold can be controlled. Of course, ratiosother than 3:2 can be utilized. This unequal circuit split may becomeadvantages, for instance, when refrigerant circuits and associatedcompression systems are of a different size and capacity, allowing fordifferent stages of capacity modulation and unloading. It has to beunderstood that a single connecting refrigerant tube 84 or 86 of alarger diameter, that leads to adjacent heat exchange tubes, can beutilized instead.

FIG. 6C is a perspective 3D view showing a detail of the manifoldstructure. The power of the inventive system is apparent, in that itprovides high flexibility control over capacity modulation by utilizingthe distinct number of heat exchange tube banks of a variable size. Asis apparent, refrigerant will flow into each of the manifolds 80 and 82,into the respective connecting refrigerant tubes 86 and 84, and theninto the associated heat exchange tube banks. This embodiment canutilize the multi-pass alternative as shown in FIG. 4B, or can beutilized in a single-pass configuration.

FIGS. 7A and 7B show the power and flexibility of the inventive conceptwherein an embodiment 90 has an inlet manifold 92 with associatedconnecting refrigerant tubes 94, an inlet manifold 96 with associatedconnecting refrigerant tubes 98, an inlet manifold 110 with associatedconnecting refrigerant tubes 112, and an inlet manifold 114 withassociated connecting refrigerant tubes 116. More than four independentrefrigerant circuits flowing through the heat exchanger 90 can beutilized.

FIG. 7C is a perspective 3D view showing the detail of the manifoldarrangement of the FIG. 7A. Additional manifolds can be interfit intoavailable space around the heat exchanger structure as shown in FIG. 7C.As illustrated, the inlet manifolds 96 and 114 are located on one sideof the core heat transfer area 21, while the manifolds 92 and 110 arepositioned on an opposed side of the core heat transfer area 21. Asbefore, refrigerant flowing through the several inlet manifolds passesinto respective connecting refrigerant tubes, and into respective heatexchange tube banks. Again, multi-pass configurations such as shown inFIG. 4B can also be utilized within this embodiment.

The connecting refrigerant tubes 33 may have different cross-sectionalareas, including (but not limited to) round, oval, rectangular, andsquare cross-sections. All these connecting refrigerant tubeconfigurations are within the scope of the invention. Furthermore, insome design arrangements, the connecting refrigerant tubes 33 may not berequired, when the heat exchange tubes 34 are bent in an alternatingpattern such that they fit directly into different inlet and outletmanifolds positioned as exhibited in multiple Figures illustrating theinvention. Such design arrangements, although feasible, may not bedesirable from manufacturability and reliability perspectives. Lastly,inlet and outlet manifolds may be positioned at the same end of the heatexchanger core 21, depending on the refrigerant pass arrangement withinthe heat exchanger core.

The inventive heat exchanger can be utilized within all types ofrefrigerant systems, such as air conditioning systems, refrigerationsystems and heat pump systems, as well as within other auxiliarysystems, such as, for instance, water cooling or heating systems,process gas/air cooling or heating systems, and oil cooling or heatingsystems. Moreover, the inventive heat exchanger can be utilized as anevaporator, condenser, gas cooler, reheat heat exchanger or any otherheat exchanger within commercial and residential air conditioning andheat pump systems, marine container units, refrigeration truck-trailerunits, merchandisers, bottle coolers, supermarket refrigeration systems,etc.

Although an embodiment of this invention has been disclosed, a worker ofordinary skill in this art would recognize that certain modificationswould come within the scope of this invention. For that reason, thefollowing claims should be studied to determine the true scope andcontent of this invention.

What is claimed is:
 1. A microchannel heat exchanger comprising: atleast two manifolds, with said at least two manifolds communicating witha respective one of a first and second plurality of heat exchange tubes;and said first and second plurality of heat exchange tubes providingmicrochannel heat exchangers within a single heat exchanger core.
 2. Themicrochannel heat exchanger as set forth in claim 1, wherein themicrochannel heat exchanger has a heat transfer surface area with saidat least two manifolds each communicating to a separate one of saidfirst and second plurality of heat transfer tubes, which extend throughsaid heat transfer surface area along a first direction, with said firstand second plurality of heat transfer tubes being generally parallel toeach other, and said heat transfer area having a second direction thatis generally perpendicular to said first direction, and heat exchangetubes from said first and second plurality of tubes being intertwinedalong said second direction.
 3. The microchannel heat exchanger as setforth in claim 2, wherein said at least two manifolds are spaced onopposed sides of said heat transfer surface area.
 4. The microchannelheat exchanger as set forth in claim 1, wherein said at least twomanifolds are connected to said plurality of heat transfer tubes byconnecting refrigerant tubes that extend from said at least twomanifolds to be connected to said heat exchange tubes in the planeperpendicular to said heat transfer surface area.
 5. The microchannelheat exchanger as set forth in claim 1, wherein there are at least fourof said manifolds, with each of said manifolds communicating withseparate heat exchange tubes.
 6. The microchannel heat exchanger as setforth in claim 5, wherein there is at least one of said at least fourmanifolds positioned on each of two lateral sides of said heat transfersurface area.
 7. The microchannel heat exchanger as set forth in claim1, wherein said at least two manifolds are one of inlet manifolds andoutlet manifolds.
 8. The microchannel heat exchanger as set forth inclaim 1, wherein each of said plurality of heat transfer tubes has aplurality of separate refrigerant channels extending into a plane ofsaid heat transfer area, and wherein said plurality of refrigerantchannels of said heat exchange tubes has a hydraulic diameter less than5 mm, and preferably less than 3 mm.
 9. The microchannel heat exchangeras set forth in claim 1, wherein each of said connecting refrigeranttubes is connected to several heat transfer tubes.
 10. The microchannelheat exchanger as set forth in claim 1, wherein said heat exchange tubesare bent or formed to fit into said at least two manifolds.
 11. Themicrochannel heat exchanger as set forth in claim 1, wherein said firstand second plurality of heat exchange tubes include different numbers ofheat exchange tubes.
 12. The microchannel heat exchanger as set forth inclaim 1, wherein there is a single refrigerant pass from an inletmanifold to an outlet manifold.
 13. The microchannel heat exchanger asset forth in claim 1, wherein there are multiple passes between an inletmanifold and an outlet manifold, with each of said inlet and outletmanifolds being subdivided to provide intermediate manifold chambers.14. The microchannel heat exchanger as set forth in claim 1, whereinsaid at least two manifolds are connected to separate independentrefrigerant circuits of a refrigerant system.
 15. The microchannel heatexchanger as set forth in claim 1, wherein said at least two manifoldsare connected to a single refrigerant circuit of a refrigerant system.